The U.S. has certified with Congress that Iran is legally in compliance on the nuclear deal, but senior Trump administration officials said both Secretary of State Rex Tillerson and President Donald Trump will couch that certification with an accusation that Iran is "unquestionably in default of the spirit of the [agreement]."

The officials pointed to "a range of malign activities" including Iran's ballistic missile development, support of militant groups in the region and Syria's Assad regime, its hostility to Israel and its continued detention of foreigners including U.S. citizens.

The officials said that moving forward the administration will "employ a strategy" that seeks to address Iran's aggressive behavior in the region.

They did not specifically outline any measures they would press for but said they expect to implement new sanctions in the near future targeting Iran's ballistic missile program and other "misbehavior" in the region.

In addition, the officials said they would seek to strengthen their relationships with partners in the region to "identify areas of ambiguity" that Iran has sought to take advantage of to potentially skirt parts of the deal.

The Trump administration's announcement tonight was part of an obligation the U.S. has under the deal to certify every 90 days that Iran is complying with the agreement. The last time the administration announced its certification of Iran's compliance, Secretary Tillerson blasted the country for its behavior in the region and said the Trump administration will address the agreement's failures to contain Iran.

Earlier Monday evening, the Foreign Minister of Iran, Mohammed Javad Zarif, took questions while at the Council on Foreign Relations and defended his country's compliance with the deal.

"I think our compliance is rather straightforward because it's not for guessing whether we have complied or not," Zarif said. "That is very clear, in black and white in the reports of the [International Atomic Energy Agency] which is hardly a sympathizer of Iran. That's so you don't need to ask me whether we've complied."

Zarif continued that Iran believes that for the U.S., including under the Obama administration, it is "more important to maintain the sanctions that remain rather than remove the sanctions."

He also argued that U.S. sanctions do not work, saying, "Let me tell you something, the United States should reconsider its approach to sanctions. Sanctions have never been an asset for the United States ... When the U.S. government started to impose nuclear sanctions on Iran we only had 200 centrifuges. When they started negotiating with us in order to remove those sanctions, we had 20,000 centrifuges. So if you want to see the result of sanctions - just 19,800 centrifuges is the net result of sanctions. So sanctions do not produce outcome."